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WSDL 2.0 - types

Jakob Jenkov
Last update: 2014-05-23

The WSDL types element describes the data types used by your web service. Most often a web service will have an input type, an output type, and perhaps a fault type. If the web service has more than one operation, then each operation may have its own input type, output type and fault type.

The data types can be declared in any language you like, as long as your web service API supports it. Data types are often specified using XML Schema though, since XML Schema is a natural fit for XML structures.

Here is an example types element that uses XML Schema to define an input type, an output type, and a fault type:

<?xml version="1.0" encoding="utf-8" ?>
<description
    xmlns="http://www.w3.org/ns/wsdl"
    targetNamespace= "http://jenkov.com/MyService"
    xmlns:tns=       "http://jenkov.com/MyService"
    xmlns:stns=     "http://jenkov.com/MyService/schema"
    . . . >

  ...

  <types>

    <xs:schema
        xmlns:xs=        "http://www.w3.org/2001/XMLSchema"
        targetNamespace= "http://jenkov.com/MyService/schema"
        xmlns:tns=       "http://jenkov.com/MyService/schema"
    >

        <xs:element name="latestTutorialRequest"
                       type="typeLatestTutorialRequest"/>

        <xs:complexType name="typeLatestTutorialRequest">
          <xs:sequence>
            <xs:element  name="date"   type="xs:date"/>
          </xs:sequence>
        </xs:complexType>

        <xs:element name="latestTutorialResponse" type="xs:string"/>

        <xs:element name="invalidDateError" type="xs:string"/>

    </xs:schema>

  </types>
  . . .
</description>

The latestTutorialRequest element is the input type. As you can see, this element is of type typeLatestTutorialRequest, and it can contain a date, telling which date to get the latest tutorial after.

The latestTutorialResponse element is the output type. The content of this element is just a string. This will contain the URL for the latest tutorial published after the given date, or an empty string if no tutorial was published after the given date.

The invalidDateError element is the fault type. The content of this element is just a string. This string can contain a textual explanation of why the date given in the input request was faulty.

XML Schema: Top Level Elements Only

In XML Schema you can define all kinds of elements and types. However, only elements declared as single elements (there can be only one), and as top level elements (not nested inside other elements), can be referred to by the WSDL 2.0 interface and operation elements. In other words, you could not use the date element by itself as an input or output type of an operation, since it is declared inside the latestTutorialRequest.

The Schema Name Space

Notice how the example shown earlier declared a name space with the prefix stns. The Schema Target Name Space (stns). This name space URI is also referenced as the target name space of the XML Schema, but here it is declared via targetNameSpace and tns, not stns.

The prefixes are not important though. The prefixes used inside XML Schema only exist within the Schema declaration, not outside. Therefore these targetNamespace and tns namespaces do not conflict with those defined in the description element.

Jakob Jenkov




Copyright  Jenkov Aps
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